Install a main site from scratch. In the database, ensure that the "tool_customlang" table is empty (delete all the records if not). As admin, go to /admin/tool/customlang/index.php In the menu, choose "English (en)" Click on the "Open language pack for editing" button. Verify that a progress bar appears and, slowly, it shows the progress. Verify that, at the end, the bar ends with "Language pack loaded 100%" texts. Verify that, at the end, the bad doesn't make any strange thing, like getting the "green" bar progressing too much or becoming bigger. Click "Back" in the browser. Click on the "Open language pack for editing" button again. Verify that, this time, it loads really faster and the bar behaves ok (as described in the fisrt load performed few steps above). Go to the database and check how many records the "tool_customlang" table has. With SQL, you can do (you may need to change or remove the "mdl_" prefix): SELECT COUNT(*) FROM mdl_tool_customlang Verify that the number is 32210 or higher.